RESUMEN
SARS-CoV-2 infection elicits robust CD8 T-cell responses, yet the identity of the mechanisms playing dominant roles in initiating the virus-specific CD8 T-cell responses are largely unknown. In the present study, we interrogate the contribution of the cDC1 subset to SARS-CoV-2-specific CD8 T-cell immunity. For this purpose, we used a novel murine line which combines the SARS-CoV-2 susceptible K18-hACE2 transgenic and the Batf3 deficient mice which lack the cDC1 subset. We demonstrate that in the absence of cDC1, viral-specific CD8 T-cell responses were severely impaired both in the draining lymph node as well as in the lungs, during the effector phase of SARS-CoV-2 infection. Furthermore, SARS-CoV-2 specific memory CD8 T-cells in the lungs and spleens were also significantly impacted, whereas humoral responses, as well as CD4 T-cells were not affected. Additionally, we demonstrate that the absence of cDC1 subset, and the consequent impaired CD8 T-cell responses, resulted in significant increase in SARS-CoV-2 viral load in the lungs. The conclusions of the study were further independently corroborated in an additional COVID-19 murine model consisting infection with a mouse-adapted SARS-CoV-2 virus. These results underscore a specific role for Batf3-dependent DC in regulating SARS-CoV-2 specific CD8 T-cell responses and may contribute to future vaccine design and immunization strategies.
Asunto(s)
COVID-19 , Animales , Ratones , Linfocitos T CD4-Positivos , Linfocitos T CD8-positivos , Células Dendríticas , SARS-CoV-2RESUMEN
The neuronopathic forms of the human inherited metabolic disorder, Gaucher disease (GD), are characterized by severe neuronal loss, astrogliosis and microglial proliferation, but the cellular and molecular pathways causing these changes are not known. Recently, a mouse model of neuronopathic GD was generated in which glucocerebrosidase deficiency is limited to neural and glial progenitor cells. We now show significant changes in the levels and in the distribution of cathepsins in the brain of this mouse model. Cathepsin mRNA expression was significantly elevated by up to approximately 10-fold, with the time-course of the increase correlating with the progression of disease severity. Cathepsin activity and protein levels were also elevated. Significant changes in cathepsin D distribution in the brain were detected, with cathepsin D elevated in areas where neuronal loss, astrogliosis and microgliosis were observed, such as in layer V of the cerebral cortex, the lateral globus pallidus and in various nuclei in the thalamus, brain regions known to be affected in the disease. Cathepsin D elevation was greatest in microglia and also noticeable in astrocytes. The distribution of cathepsin D was altered in neurons in a manner consistent with its release from the lysosome to the cytosol. Remarkably, ibubrofen treatment significantly reduced cathepsin D mRNA levels in the cortex of Gaucher mice. Finally, cathepsin levels were also altered in mouse models of a number of other sphingolipidoses. Our findings suggest the involvement of cathepsins in the neuropathology of neuronal forms of GD and of other lysosomal storage diseases, and are consistent with a crucial role for reactive microglia in neuronal degeneration in these diseases.
Asunto(s)
Catepsinas/genética , Catepsinas/metabolismo , Enfermedad de Gaucher/metabolismo , Expresión Génica , Esfingolipidosis/genética , Animales , Encéfalo/metabolismo , Modelos Animales de Enfermedad , Femenino , Enfermedad de Gaucher/genética , Humanos , Masculino , Ratones , Ratones Noqueados , Neuronas/metabolismo , Isoformas de Proteínas/genética , Isoformas de Proteínas/metabolismo , Transporte de Proteínas , Esfingolipidosis/metabolismoRESUMEN
Gaucher disease (GD), the most common lysosomal storage disorder (LSD), is caused by defects in the activity of the lysosomal enzyme, glucocerebrosidase, resulting in intracellular accumulation of glucosylceramide (GlcCer). Neuronopathic forms, which comprise only a small percent of GD patients, are characterized by neurological impairment and neuronal cell death. Little is known about the pathways leading from GlcCer accumulation to neuronal death or dysfunction but defective calcium homeostasis appears to be one of the pathways involved. Recently, endoplasmic reticulum stress together with activation of the unfolded protein response (UPR) has been suggested to play a key role in cell death in neuronopathic forms of GD, and moreover, the UPR was proposed to be a common mediator of apoptosis in LSDs (Wei et al. (2008) Hum. Mol. Genet. 17, 469-477). We now systematically examine whether the UPR is activated in neuronal forms of GD using a selection of neuronal disease models and a combination of western blotting and semi-quantitative and quantitative real-time polymerase chain reaction. We do not find any changes in either protein or mRNA levels of a number of typical UPR markers including BiP, CHOP, XBP1, Herp and GRP58, in either cultured Gaucher neurons or astrocytes, or in brain regions from mouse models, even at late symptomatic stages. We conclude that the proposition that the UPR is a common mediator for apoptosis in all neurodegenerative LSDs needs to be re-evaluated.